System for starting and operating gaseous electric discharge devices



April 25, 1933.

Fig.1-

J. D. FORNEY 1,905,840

Filed Nov. 29, 1929 Fig.2 4

Patented Apr. 25, 1933 UNITED' STATES PATENT OFF-ICE JOHN D. FORNEY, OF CHATHAM, NEW JERSEY, ASSIGNOR TO GENERAL ELEG'IRIO VAPOR LAMP COMPANY, OF HOIBOKEN, JERSEY, A CORPORATION OF NEW JERSEY SYSTEM FOR sTAnTING Ann orERATfNe GASEOUS ELECTRIC msommen nEvIoEs Application filed November 29, 1929. Serial No. 410,488.

The present invention relates to electric gaseous discharge devices, and particularly to method and means for the starting and operation of discharge devices having thermionic cathodes.

The invention consists in a new and novel method of operation and in a novel combination of elements as hereinafter set forth and claimed.

A particular object of'the invention is to provide a method and means for automatically'regulating' the heat supplied to a thermionic cathode. Other objects and advantages of the invention will appear from the fo lowing detailed specification or from an insgection of the accom anying drawing.

well known type 0 low voltage gaseous discharge device utilizes an oxide-coated cathode which is raised to an electron emitting temperature by means of a suitable filamentary heater which is operated at a otential lower than the ionizing potentia of the gaseous atmosphere present in the device. This filamentary heater has heretofore been supplied with energy from a constant potential source, so that the heating of the cathode thereby is approximately constant at all times. This has not been entirely desirable, since the cathode of this type of device must be heated before -a discharge is initiated, during which time the filamentary heater is the sole source of heat, whereas during operation the discharge contributes materially to the heating of said cathode. In order to shorten the time "required to heat the cathode to an electron emitting condition, during which time the discharge cannot be safely started, it is highly desirable to operatethe/ filamentary heater during this interval with a higher current input than is necessary or desirable after the discharge is started. ,I have discovered that this result may be automatically attained by so connecting the filamentary heater that it is subject to the voltage regulation provided to stabilize the discharge. When so connected a voltage considerably higher than normal will be impressed upon the filamentary heater during the starting period, which will be decreased to normal potential as soon as the discharge and designed for operation on alternating current, and

Fig. 2'is a schematic diagram of a variation of. the circuit of Fig. 1. *i-IAs shown in the drawing, with particular reference to Fig. 1, an electric gaseous dis-\ 'chargedevice 1 has a cathode 2 of nickel or other suitable material which is preferably coated with an alkaline or alkaline earth oxide, and which is provided with afila-mentary heater 3 of tungsten or the like, While spaced apart therefrom are the anodes 4 or iron,

graphite or other suitable material. This device contains a suitable gaseous atmosphere, such as neon or mercury vapor. The anodes 4 areeach connected'through a lead 5 and a resistance 6 to opposite ends of an autotransformer 7, which may, if desired, supply energy-to a plurality of discharge devices 1, while the cathode 2 is connected through a lead 8 and an inductance (9 to a mid-point ofsaid autotransformer. -Leads 10 connect said autotransformer to a suitable source of alternating current. Each end of the primary of the filament supply transformer 11 is connected to a lead 5 at a point between the anode 4 and resistance 6, while the secondary of said transformer has one end connected to the cathode lead 8 and the other to one end of the filamentary heater 3,

the other end of said filamentary heater being connected to the cathode 2. For starting purposes a connection is made from the cathode lead 8 through a mercury switch or shifter 12, resistance 13 and resistance 14 to one end of the autotransformer 7. A bimetallic element 15 which is in thermal relation to said resistance 14 is connected thereto at one end and is adapted to short circuit saidresistance after current has passed therethrough for a time interval which is made to equal the timerequired to heat the cathode 2 to a safe operatmg temperature. The shifter 12 isnormally in a circuit closing position, but has an armature in magnetic relation to the inductance 9 whereby it is moved to an open circuit position when said inductance is energized, the resistance 14 being of such a value, however, that the current therethrough is insuflicient to operate said shifter.

In the use and operation of this device, upon the application of a suitable alternating current potential to the leads 10 a potentia difference is created between. the anodes 4 and the cathode 2 which is, however, insufiicient to initiate a discharge in said device. A-potential is likewise applied to the primary of the transformer 11, the induced potential in the secondary thereof causing a How of current through the circuit passing from one end of said secondary through the filamentary heater 3, cathode 2, and cathode lead 8 to the other end of said secondary. The resulting primary current of said transformer 11 is drawn through the resistances .6, in series, but since this current is small as compared to the discharge current, the potential drop therein is small, so that substantially the full voltage of the autotransformer 7 is impressed on the primar of the transformer 11. The heating of t e cathode 2 therefore progresses at a ra id rate. At the same time a current flows rom the mid-point of the autotransformer 7 through the inductance 9, shifter 12, resistance 13 and resistance 14 to one end of said auto-transformer. The heat generated by this current in the resistance 14 slowly warps the bimetallic element 15 until eventuall it short circuits said resistance, the increase current which thereupon fiows through the inductance 9 being then suflicient to actuate the shifter 12 to an open position. As the circuit is thus interrupted the collapsing magnetic field about said inductance *9 creates a voltage surge which initiatesthe discharge in the device 1, the discharge current thereupon maintaining the shifter '12 in the open circuit position. This discharge current, which passes alternately through the resistances 6 during nate half 0 'cles produces a considerab e voltage drop t erein. The otential applied to the transfrrmer 11 is t ereby reduced say 10-20% with the ensuing decrease in current flow through the filamentary heater 3 so that the heating efiect thereof, and the wattage consumed, is materially reduced so long as the discharge is maintained.

With the connections shown in Fig. 2, in which a resistance 6' in series with one of the leads 10 supplants the two resistances 6 of Fig. 1, it is possible to omit the separate filament supply transformer 11, a low voltage altersecondary 11' on the auto-transformer 7 bein utilized instead.

he operation of this circuit during the startin period is substantially the same as that o ig. 1, the voltage drop in theresistance 6 being small due to the relatively low wattage consumed by the filament 3 and the heating resistance 14:. Upon initiation of the discharge in the device 1, however, the resistance 6' consumes an appreciable portion of the line potential, say 20% or more, so that the excitation potential applied to the autotransformer .7 is decreased y that amount. This supplies the needed regulation for the discharge and likewise reduces the potential of 'the secondary 11', thereby decreasing the wattage supplied to the filament 3 during maintenance of the discharge. This circuit has several advantages over that of Fig. 1. As will be evident, a greater degree of regulation of the filament current is obtainable with this circuit than is possible with the circuit of Fig. 1. The elimination of the separate filament transformer made possible by this circuit, is also desirable in many cases. Furthermore, this circuit reduces the potential supplied to the inactive anode and thereby tends to decrease the hi hly undesirable current from anode to ano e.

While I have illustrated and described my invention by reference to particular embodiments thereof it is to be understood that it is not limited thereto, and that various additions, changes and substitutions, within the scope of the appended claims, may be made therein without departing from the spirit of my invention.

I claim:

1, In combination, an electric gaseous discharge device having a. cathode adapted to emit electrons when heated, means comprising an electric heater to heat said cathode, and means to vary the energy supplied to said cathode heating means.

'2. In combination, an electric gaseous discharge device havingla cathode adapted to emit electrons when eated, means com rising an electric heater to heat said cath e at a given rate, and means to decrease said rate during maintenance of a discharge in said device.

3. In combination, an electric gaseous discharge device having a cathode adapted to emit electrons when heated, means comprising an-electric heater to heat said cathode at a given rate, and means responsive to the flow of the discharge current to decrease the rate of heating by said heating means during maintenance of a discharge in said device.

4. In combination, an electric gaseous discharge device having a cathode adapted to emit electrons when heated, an electric heater, for sand cathode, and means responsive to the flow of. the discharge current to. decrease the potential applied to said heater.

5. In combination, an electric gaseous discharge device having a cathode adapted to emit electrons when heated, an electric heater for said cathode, and an impedance in series with said discharge device and with said heater.

6. In combination, an electric gaseous discharge device having a cathode adapted to emit electrons when heated, means to heat said cathode, means to initiate a discharge in said device, means to delay the operation of said last mentioned means until said cathode is at operating temperature, and means for varying the energy supplied to said cathode heating means.

7. In combination, an electric gaseous discharge device having a cathode adapted to emit electrons when heated, an electric heater for said cathode. means to initiate a discharge in said device, means to delay the operation of said last mentioned means until said cathode is at operating temperature, and means responsive to the flow of the discharge current to decrease the potential applied to said heater.

8. In combination with an electric gaseous discharge device having a cathode adapted to em it clectrons when heated and an electric heater for said cathode, a transformer supplying energy to said discharge device and to said heater, and an impedance in the primary circuit of said transformer.

9. The method of operating an electric gaseous discharge device having a thermionic cathode which comprises indirectly heating sald cathode at a given rate before initiating a discharge in said device, and decreasing said rate of heating after the initiation of a. discharge therein.

10. The method of operating an electric gaseous discharge device having a thermionic cathode which comprises indirectly heating said cathode at a given rate before initiating a discharge in said device, and availing of the voltage drop in an impedance due to the flow of the discharge current to reduce said rateof heating during maintenance of a discharge in said device.

Signed at Hoboken, in the coun of Hudson and State of New Jersey, this th day. of

Kin-ember, A. D. 1929.

a D. ITORNEY. 

